MOSCOW (AP) - Russian opera diva Galina Vishnevskaya, who conquered audiences all over the world with her rich soprano, has died. Vishenvskaya, widow of famed cellist Mstislav Rostropovich, was 86.

Moscow's Opera Center, which Vishnevskaya created, said the singer died Tuesday in the Russian capital. It didn't give the cause.

Vishnevskaya joined Moscow's Bolshoi Theater in 1952, making her debut as Tatiana in Yevgeny Onegin. She performed dozens of soprano roles in Russian and European opera classics.

She made her Metropolitan Opera debut as Aida in 1961 and first sang Liu in Turandot in La Scala in 1964.

From 1955 and until his death in 2007, Vishnevskaya was married to Rostropovich.

They frequently performed together, and used their star status in the Soviet Union to help friends in trouble, including writer Alexander Solzhenitsyn whom they sheltered at their dacha when he was facing official reprisals.

After Solzhenitsyn was expelled from the country, Vishnevskaya and Rostropovich left the Soviet Union with their two daughters in 1974. They lived in Paris and then Washington, and were stripped of their Soviet citizenship in 1978.

They returned to Russia after the Soviet collapse and became involved in public activities and charitable work.

Vishnevskaya, survived by her two daughters, will be buried Friday at Moscow's Novodevichy Cemetery alongside her husband.

President Vladimir Putin sent his condolences, praising the singer's "remarkable talent, strong will, nobleness and self-dignity."